1. Field of the Invention
The invention relates to the field of digital watermarks, and more particularly, to non-repudiation watermarking protection based on public and private keys.
2. Description of the Related Art
With the recent growth of networked multimedia systems, techniques are needed to prevent (or at least deter) the illegal copying, forgery and distribution of media content, such as digital audio, images and video. Many approaches are available for protecting digital data; these include encryption, authentication and time stamping. It is also desirable to determine where and by how much the digital data has been changed from the original.
One way to improve a claim of ownership over digital data, for instance, is to embed a low-level signal or structure directly into the digital data. For example, a digital watermark uniquely identifies the owner and can be easily extracted from the digital data. If the digital data is copied and distributed, the watermark is distributed along with the data. This is in contrast to the (easily removed) ownership information fields allowed by the MPEG-2 syntax.
Most digital watermark schemes depend on a trusted third party to verify the authenticity of the watermark. The services of the trusted third party may be employed for storing digital watermark keys in escrow, wherein the keys are presented upon demand if there is a dispute. See, for example, D. Augot, J-M. Boucueau, J. F. Delaigle, C. Fontaine, and E. Goray, “Secure Delivery of Images over Open Networks,” Proceedings of the IEEE, Vol. 87, No. 7, July 1999, which publication is incorporated by reference herein.
However, situations may arise, particularly where the value of the media content is very high, where a trusted third party cannot be found, at least not one that can be trusted by both parties. There is a need in the art, then, for systems that do not require a trusted third party for watermark key escrow. Specifically, there is a need in the art for digital watermarks that are non-repudiation watermarks and where the source of the embedded watermark can be accurately traced.